Recent evidence supports the recognition that HPV infection is a major risk factor for head and neck squamous cell carcinoma (HNSCC), in particular oropharyngeal SCC. High-risk HPV16 is by far the most frequent, ~90%, HPV type detected in HNSCC. Epidemiological data indicate that the prevalence of HPV-positive HNSCC has rapidly increased by about 3-fold in the past three decades in the United States and Europe (2-4). Based on these alarming numbers, it has been suggested that an epidemic of HPV-positive HNSCC will emerge in the near future. Additional work to probe the mechanism of action of HPV-induced tumorigenesis is needed to reveal actionable druggable targets for the development of HPV-directed anti-cancer therapeutics. p300, a transcriptional co-activator, controls gene transcription through multiple mechanisms; as an acetyltransferase to acetylate histones and transcription factors, as a scaffold for transcription factors on chromatin, and as a bridge to connect transcription factor to the transcriptional machinery. Interestingly, single allee knockout of p300 has distinct transcriptional phenotypes revealing that promoter bound transcription factors are likely to be in competition to recruit limited amounts of p300. HPV16E6 was reported to bind to p300 at the CH1, CH3, and C-terminus domains whereas HPV16E7 binds to the CH1 and CH3 domains. Since p300 is a limited resource, it is likely that HPV16E6 and HPV16E7 co-opt host p300 to control p300 function in HPV16-positive HNSCC cells. Our main hypothesis is that restoration of host p300 function may be an approach to reactivate p53/pRb and reverse HPV16-induced transformation of epithelial cells. In this application, biochemical and chemical approaches will be used to probe the interaction between HPV16E6/E7 and p300 in HPV16-positive HNSCC. The molecular mechanism of action for p300 domain ligands will be defined in vitro and in vivo.